An epitaxial growth technology is a technology for epitaxially growing a single-crystal thin film layer in vapor phase, which is utilized in manufacture of an integrated circuit such as a bipolar transistor or an MOSLSI, and it is a very important technology since a uniform single crystal thin film can be grown on a clean semiconductor single crystal substrate in accordance with a crystal orientation of the substrate or a precipitous impurity gradient of a junction having a large dopant concentration difference can be formed.
As apparatuses that perform such epitaxial growth, three types, i.e., a vertical type (a pancake type), a barrel type (a cylinder type) and a lateral type are general. These growth apparatuses have a common basic principle. Each growth apparatus is configured to include a reaction chamber including an epitaxial growth susceptor on which a single-crystal silicon substrate is placed, heating means formed of, e.g., a halogen lamp provided outside the reaction chamber and others, and an apparatus that processes wafers one by one in vertical type apparatuses is called a single-wafer processing epitaxial growth apparatus.
For example, this single-wafer processing epitaxial growth apparatus will now be described with reference to FIG. 4. FIG. 4 is a schematic view showing an example of a conventionally utilized general single-wafer processing epitaxial growth apparatus.
This single-wafer processing epitaxial growth apparatus 41 has a reaction chamber 43 in which a silicon substrate 42 on which an epitaxial layer is piled up on a surface thereof is arranged therein, and a gas introduction opening 44 from which a raw material gas/carrier gas is introduced to the reaction chamber 43 and a gas discharge opening 45 from which the gas is discharged are provided. Further, the reaction chamber 43 includes a susceptor 46 on which the silicon substrate 42 is placed.
Furthermore, at least heating means 48, e.g., a halogen lamp for heating the silicon substrate 42 is provided outside the reaction chamber 43.
Moreover, giving a description on a general method for forming an epitaxial layer on the silicon substrate 42 by using the single-wafer processing epitaxial growth apparatus 41 depicted in FIG. 4, this method is carried out by first placing the single-crystal silicon substrate 42 on the susceptor 46, heating the substrate 42 to a predetermined temperature by the heating means 48 while rotating the silicon single crystal substrate 42 by using a support shaft 49 that supports the susceptor 46 and a non-illustrated rotation mechanism that rotates the support shaft 49 (rotates the same on its axis), and supplying a raw material gas such as trichlorosilane diluted with a carrier gas such as hydrogen into the reaction chamber 43 from the gas introduction opening 44 for a predetermined time at a predetermined flow quantity. As a result, a silicon epitaxial wafer having an epitaxial layer piled up on the substrate 42 can be obtained.
Although the quality has been conventionally improved in manufacture of the silicon epitaxial wafer, a pocket formed in the susceptor is deformed as one of such improving methods. For example, Japanese Patent Application Laid-open No. S59-50095 discloses various susceptors. Such susceptors can be roughly classified into a type that supports a substantially entire back surface of a substrate and a type that supports a part of the substrate alone (see, e.g., Japanese Patent Application Laid-open No. S59-50095, Japanese Patent Application Laid-open No. H5-238882, Japanese Patent Application Laid-open No. H7-58039, and Japanese Patent Application Laid-open No. 2004-319623).
As the type that supports a substantially entire back surface of a substrate, there are a susceptor having a configuration that a pocket has a flat bottom surface, a susceptor having a configuration that a cylindrical convex portion having a diameter smaller than a diameter of a substrate to be placed is formed on a bottom surface of a pocket, a susceptor having a configuration that a portion that comes into contact with the substrate has a mesh-like shape, and others.
However, this kind of susceptor comes into contact with the substantially entire back surface of the substrate, and hence it has a problem that a placing surface (the back surface) of the substrate is damaged. Further, when scratches remain on the back surface of the substrate, they become a cause of particle generation in a subsequent device manufacturing process.
On the other hand, as the type that supports a part of the substrate alone, there are a susceptor having a configuration that a ring-like convex portion is formed at an inner side apart from an edge portion of a substrate to be placed, and a susceptor having a configuration that a concave portion is formed at a central portion of a pocket to hold an outer peripheral portion (an inner side apart from an edge portion) of the substrate where a device is not fabricated.
However, although such a type of susceptor does not damage the entire back main surface of the substrate, but it supports the substrate at a part alone, and hence there is a problem that a scratch at a contact portion is deep, the substrate bends or slip occurs from the edge portion of the substrate.
Further, Japanese Patent Application Laid-open No. 2005-235906 discloses a susceptor which has a configuration that an inclined surface is formed at an outer periphery of a pocket and which supports a substrate in such a manner that an edge portion of the substrate comes into contact with the inclined surface to reduce scratches generated on a back surface of the substrate. Furthermore, Japanese Patent Application Laid-open No. 2003-100855 discloses that a silicon oxide film is formed on a back surface of a substrate so as to prevent the back surface of the substrate from being damaged by lift pins.
However, even though the ingenuity is exercised with respect to the substrate supporting method in this manner, the problem of particle generation in the device manufacturing process still arises.